Coated substrates, for example, coated cutting inserts, are used in material removal applications. The coating layers typically comprise hard refractory materials that exhibit the property of wear resistance. One purpose of such coatings on cuttings insert is to lengthen the service life of the cutting inserts.
One hard refractory material that has been found to be useful as a coating layer material, or as part of a scheme of coating layers, is titanium oxycarbonitride, which is sometimes referred to by the generic formula Ti (C,N,O). Another is titanium aluminum oxycarbonitride, which is sometimes referred to by the generic formula (Ti, Al)(C,N,O). Examples of coatings comprising at least one of these materials can be found in U.S. Pat. No. 4,714,660 to Gates, Jr.; U.S. Pat. No. 5,700,569 to Ruppi; U.S. Pat. No. 6,284,356 B1 to Kiriyama; U.S. Pat. No. 6,436,519 B2 to Holzschuh; U.S. Pat. No. 6,472,060 B1 to Ruppi et al.; U.S. Pat. No. 6,620,498 B2 to Ruppi et al.; U.S. Pat. No. 7,718,226 B2 to Ruppi; U.S. Pat. No. 7,785,665 B2 to Gates, Jr. et al.; and U.S. Pat. Application Publication No. US 2007/0298232 A1 of McNerny et al.
Although the usefulness of coatings comprising titanium oxycarbonitride and/or titanium aluminum oxycarbonitride has been demonstrated, improvements are still needed in the wear resistance they provide. The present invention addresses this need.